PHP句子边界包括空行？

Question

这是 SO 上 PHP sentences boundaries question 的扩展。

我想知道如何更改正则表达式以保留换行符。

示例代码逐句拆分一些文本，删除一个句子，然后重新组合：

<?php
$re = '/# Split sentences on whitespace between them.
    (?<=                # Begin positive lookbehind.
      [.!?]             # Either an end of sentence punct,
    | [.!?][\'"]        # or end of sentence punct and quote.
    )                   # End positive lookbehind.
    (?<!                # Begin negative lookbehind.
      Mr\.              # Skip either "Mr."
    | Mrs\.             # or "Mrs.",
    | Ms\.              # or "Ms.",
    | Jr\.              # or "Jr.",
    | Dr\.              # or "Dr.",
    | Prof\.            # or "Prof.",
    | Sr\.              # or "Sr.",
    | T\.V\.A\.         # or "T.V.A.",
                        # or... (you get the idea).
    )                   # End negative lookbehind.
    [\s+|^$]            # Split on whitespace between sentences/empty lines.
    /ix';

$text = <<<EOL
This is paragraph one. This is sentence one. Sentence two!

This is paragraph two. This is sentence three. Sentence four!
EOL;

echo "\nBefore: \n" . $text . "\n";

$sentences = preg_split($re, $text, -1);

$sentences[1] = " "; // remove 'sentence one'

// put text back together
$text = implode( $sentences );

echo "\nAfter: \n" . $text . "\n";
?>

运行这个，输出是

Before: 
This is paragraph one. This is sentence one. Sentence two!

This is paragraph two. This is sentence three. Sentence four!

After: 
This is paragraph one. Sentence two!
This is paragraph two. This is sentence three. Sentence four!

我试图让“之后”文本与“之前”文本相同，只是删除了一个句子。

After: 
This is paragraph one. Sentence two!

This is paragraph two. This is sentence three. Sentence four!

我希望这可以通过正则表达式调整来完成，但我错过了什么？

Answer 1

模式的结尾应替换为：

  (?:\h+|^$)          # Split on whitespace between sentences\/empty lines.
/mix';

见IDEONE demo

请注意，[\s+|^$] 真正匹配空格（水平和 垂直，如换行符）、+、|、^ 和 $ 符号，因为它是一个 字符类。

而不是字符类，一个组（更好，这里不捕获）是必要的。在组内（标有(...)），| 用作交替运算符。

我建议不要使用\s，而是使用匹配水平空格（无换行符）的\h。

如果没有使用/m 多行修饰符，^$ 只会匹配空字符串。所以，我在选项中添加了/m 修饰符。

请注意，我必须在最后一条评论中转义 /，否则会出现正则表达式不正确的警告。或者，使用不同的正则表达式分隔符。